MD2(3)

NAME
MD2Init, MD2Update, MD2Final, MD2End, MD2File, MD2Data - calculate the RSA Data Security, Inc., “MD2” message digest

LIBRARY
libc

SYNOPSIS
#include <sys/types.h>
#include <mdX.h>
void
MD2Init(MD2_CTX *context);
void
MD2Update(MD2_CTX *context, const unsigned char *data, unsigned int len);
void
MD2Final(unsigned char digest[16], MD2_CTX *context);
char *
MD2End(MD2_CTX *context, char *buf);
char *
MD2File(const char *filename, char *buf);
char *
MD2Data(const unsigned char *data, unsigned int len, char *buf);

DESCRIPTION
The MD2 functions calculate a 128-bit cryptographic checksum (digest) for any number of input bytes. A cryptographic checksum is a one-way hash-function, that is, you cannot find (except by exhaustive search) the input corresponding to a particular output. This net result is a ``fingerprint'' of the input-data, which doesn't disclose the actual input.

The MD2 routines should not be used for any security-related purpose.

The MD2Init(), MD2Update(), and MD2Final() functions are the core functions. Allocate an MD2_CTX, initialize it with MD2Init(), run over the data with MD2Update(), and finally extract the result using MD2Final().

MD2End() is a wrapper for MD2Final() which converts the return value to a 33-character (including the terminating '\0') ASCII string which represents the 128 bits in hexadecimal.

MD2File() calculates the digest of a file, and uses MD2End() to return the result. If the file cannot be opened, a null pointer is returned. MD2Data() calculates the digest of a chunk of data in memory, and uses MD2End() to return the result.

When using MD2End(), MD2File(), or MD2Data(), the buf argument can be a null pointer, in which case the returned string is allocated with malloc(3) and subsequently must be explicitly deallocated using free(3) after use. If the buf argument is non-null it must point to at least 33 characters of buffer space.

SEE ALSO
md2(3), B. Kaliski, The MD2 Message-Digest Algorithm, RFC 1319. RSA Laboratories, Frequently Asked Questions About today's Cryptography.

HISTORY
These functions appeared in NetBSD 1.3.

AUTHORS
The original MD2 routines were developed by RSA Data Security, Inc., and published in the above references. This code is a public domain implementation by Andrew Brown.

BUGS
No method is known to exist which finds two files having the same hash value, nor to find a file with a specific hash value. There is on the other hand no guarantee that such a method doesn't exist.